Leaving a "request changes" review only applies the S-waiting-on-review
label if the review comes from somebody who is assigned to the PR. However, this means we don't get that benefit on repos where auto-assign isn't enabled. Could this be loosened so a relabel happens when done by anybody with write access, rather than restricted to the assignee? I think removing the assignment check should suffice here since users without write access can't change leave the red/green reviews.
This could also be made configurable. IMO this probably isn't necessary since in practice leaving a "request changes" review usually always indicates action required, regardless of whether the assignee is up to date, and "comment" is used for things that aren't blocking.
Example PR: rust-lang/libc#4615